[clang] [clang-format] clang-format-ignore: Add support for double asterisk patterns (PR #110560)

[Owen Pan via cfe-commits]

================
@@ -164,6 +164,40 @@ TEST_F(MatchFilePathTest, Path) {
   EXPECT_FALSE(match("foo\\", R"(foo*\)"));
 }
 
+TEST_F(MatchFilePathTest, DoubleAsterisk) {
+  EXPECT_TRUE(match("a/b/c/d.cpp", "**b**"));
+  EXPECT_TRUE(match("a/b/c/d.cpp", "**/b/**"));
+  EXPECT_TRUE(match("a/b/c/d_e.cpp", "**d_*"));
+  EXPECT_TRUE(match("a/b/c/d_e.cpp", "**/d_*"));
+  EXPECT_TRUE(match("a/b/c/d_e.cpp", "**d_**"));
+  EXPECT_TRUE(match("a/b/c/d_e.cpp", "**/d_**"));
+
+  EXPECT_TRUE(match("a/b/c/d_e.cpp", "**/b/c/**"));
+
+  EXPECT_TRUE(match("a/b/c/d_e.cpp", "a/**/b/c/d_e.cpp"));
+  EXPECT_TRUE(match("a/b/c/d_e.cpp", "a/**/c/d_e.cpp"));
+  EXPECT_TRUE(match("a/b/c/d_e.cpp", "a/**/b/**/d_e.cpp"));
+  EXPECT_TRUE(match("a/b/c/d_e.cpp", "**/b/**/d_e.cpp"));
+  EXPECT_TRUE(match("a/b/c/d_e.cpp", "a/**/**/b/**"));
+
+  EXPECT_FALSE(match("a/b/c/d_e.cpp", "**/d"));
+  EXPECT_FALSE(match("a/b/c/d_e.cpp", "**/b/d"));
+  EXPECT_FALSE(match("a/b/c/d_e.cpp", "**/b/d/**"));
+  EXPECT_FALSE(match("a/b/c/d_e.cpp", "**/b/c/"));
+
+  // Multiple consecutive asterisks are treated as **
+  EXPECT_TRUE(match("a/b/c/d.cpp", "***b****"));
+  EXPECT_TRUE(match("a/b/c/d.cpp", "****/b/***"));
+  EXPECT_TRUE(match("a/b/c/d_e.cpp", "***d_**"));
+  EXPECT_TRUE(match("a/b/c/d_e.cpp", "****/d_*"));
+  EXPECT_TRUE(match("a/b/c/d_e.cpp", "***/b/c/*****"));
+
+  EXPECT_FALSE(match("a/b/c/d_e.cpp", "*****/d"));
+  EXPECT_FALSE(match("a/b/c/d_e.cpp", "***/b/d"));
+  EXPECT_FALSE(match("a/b/c/d_e.cpp", "*****/b/d/***"));
+  EXPECT_FALSE(match("a/b/c/d_e.cpp", "***/b/c"));
----------------
owenca wrote:

> > unless there's a good reason
> 
> This came up as I have been working on adding support for clang-format within [AMD's PAL repository](https://github.com/GPUOpen-Drivers/pal) and found clang-format-ignore to be extremely limiting.

How is it _extremely_ limited? Just because it doesn't support `**` in the middle of the pathnames? How did you manage before clang-format gained the `.clang-format-ignore` functionality?

> There are 2 key reasons I am adding this feature:
> 
> * Simplifying Subdirectory Exclusion: `**` allows for easy exclusion of entire subdirectories. Currently you need to specify each depth level in a subdirectory individually.

We have `DisableFormat` for that.

> * Pattern-Based File Ignoring: `**` simplifies ignoring specific file patterns that may appear at any level within a directory tree, which is especially useful when the exact depth of these files can vary

I was conscious of this use case, but you can do something like `find . -name dont-format-me >> .clang-format-ignore` even though it's less than ideal.

> > and strong demand for it.
> 
> How do we gauge how much of a demand there is for this feature?

See https://github.com/llvm/llvm-project/issues/52975#issue-1093103318.

If we were to add `**` to match gitignore, we should also handle it at the beginning and the end of a pathname.

https://github.com/llvm/llvm-project/pull/110560